The surging demand for rechargeable batteries in portable electronics and electric vehicles has stimulated extensive studies on various lithium-based electrode materials. Sulfur is a well-researched material that is nontoxic to the environment and earth-abundant. It can host two lithium ions (Li+) non-topotactically, and exhibits a high theoretical capacity of 1675 mAh/g, almost 10 times that of commercially popular transition metal based intercalating cathode materials, such as LiCoO2. In terms of gravimetric energy density, at 2.1 V versus Li/Li+, lithium-sulfur (Li—S) batteries possess about 5 times the energy density compared to those based on LiCoO2.
However, sulfur and its insoluble by-product compounds, such as Li2S2 and Li2S, are poor electronic and ionic conductors (electronic insulators), which significantly reduces the effectiveness of Li—S batteries. Furthermore, these deficiencies necessitate positioning sulfur-based electrodes in constant and intimate contact with liquid electrolyte to enhance effective Li+ conductivity, which otherwise leads to a rapid degradation of capacity and cycle life. In addition, the capacity of conventional Li—S batteries rapidly decay with the number of charge/discharge cycles due to rapid dissolution of soluble lithium polysulfides Li2SX (4≤X≤8) into interfacial bulk liquid electrolyte, and/or via volume expansion-induced mechanical failures within the electrode structures that couple with and led to degrading electronic conductivity across the electrode. To retard the loss of S into the electrolyte solution, many strategies have been proposed and undertaken, such as modifying the electrolyte to be a poorer solvent for sulfur species, and engineering a better electrode and operating voltage of the electrochemical system, as described, for example, in the articles by Z. Lin, Z. C. Liu, W. J. Fu, N. J. Dudney and C. D. Liang, in Angewandte Chemie International Edition, 2013, 52, 7460-7463; by E. Peled, Y. Sternberg, A. Gorenshtein and Y. Lavi, in the Journal of the Electrochemical Society, 1989, 136, 1621-1625; by S. E. Cheon, K. S. Ko, J. H. Cho, S. W. Kim, E. Y. Chin and H. T. Kim, in the Journal of the Electrochemical Society, 2003, 150, A800-A805; by L. X. Yuan, J. K. Feng, X. P. Ai, Y. L. Cao, S. L. Chen and H. X. Yang, in Electrochemistry Communications, 2006, 8, 610-614; by J. H. Shin and E. J. Cairns, in the Journal of Power Sources, 2008, 177, 537-545; by Z. W. Seh, W. Li, J. J. Cha, G. Zheng, Y. Yang, M. T. McDowell, P.-C. Hsu and Y. Cui, in Nature Communications, 2013, 4, 6; by J. Wang, S. Y. Chew, Z. W. Zhao, S. Ashraf, D. Wexler, J. Chen, S. H. Ng, S. L. Chou and H. K. Liu, in Carbon, 2008, 46, 229-235; and by Y. S. Su, Y. Z. Fu, T. Cochell and A. Manthiram, in Nature Communications, 2013, 4, 2985. ‘Solvent-in-Salt’ electrolytes with ultrahigh salt concentration can also be used to achieve a high-energy rechargeable battery, for example as described in the articles by L. M. Suo, Y. S. Hu, H. Li, M. Armand and L. Q. Chen, in Nature Communications, 2013, 4; and by Y. Sun, L. Zhao, H. L. Pan, X. Lu, L. Gu, Y. S. Hu, H. Li, M. Armand, Y. Ikuhara, L. Q. Chen and X. J. Huang, in Nature Communications, 2013, 4. Strategies for inhibiting undesirable polysulfide dissolution reactions via modifying the charging condition were developed to obtain improved cycle life (>500 cycles), and additives like graphene, mesoporous carbon, and conductive polymers were exploited to facilitate efficient electron conduction, as described in the articles by H. L. Wang, Y. Yang, Y. Y. Liang, J. T. Robinson, Y. G. Li, A. Jackson, Y. Cui and H. J. Dai, in Nano Letters, 2011, 11, 2644-2647; by M. K. Song, Y. G. Zhang and E. J. Cairns, in Nano Letters, 2013, 13, 5891-5899; by N. Jayaprakash, J. Shen, S. S. Moganty, A. Corona and L. A. Archer, in Angewandte Chemie International Edition, 2011, 50, 5904-5908; by Y. Z. Fu and A. Manthiram, in the Royal Society of Chemistry Advances, 2012, 2, 5927-5929; by X. Liang, Y. Liu, Z. Y. Wen, L. Z. Huang, X. Y. Wang and H. Zhang, in the Journal of Power Sources, 2011, 196, 6951-6955; by H. K. Song and G. T. R. Palmore, in Advanced Materials, 2006, 18, 1764; by J. L. Wang, J. Yang, J. Y. Xie and N. X. Xu, in Advanced Materials, 2002, 14, 963; and by Y. Yao, N. Liu, M. T. McDowell, M. Pasta and Y. Cui, in Energy & Environmental Science, 2012, 5, 7927. By encapsulating sulfur in TiO2 nanoshells with pre-existing void, the ˜80% volume expansion of sulfur in lithiation can be accommodated and this yolk-shell structure can also restrict the intermediate polysulfides to reside within the structure, so the battery could run over 1000 cycles with good capacity retention, as described in Z. W. Seh, W. Li, J. J. Cha, G. Zheng, Y. Yang, M. T. McDowell, P.-C. Hsu and Y. Cui, in Nature Communications, 2013, 4, 6. However, although recent technological progress has been made in Li—S battery performance according to G. Y. Zheng, Y. Yang, J. J. Cha, S. S. Hong and Y. Cui, in Nano Letters, 2011, 11, 4462-4467, manufacturing such improved Li—S battery system at mass-production levels, employing a scalable and cost-effective synthesis is still yet to be demonstrated, until the present invention.